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[en] It is the purpose of this paper to prove that a preferred space direction is coupled with each tachyon and, consequently, scalar tachyons, are impossible in principle. Even the notion of a scalar faster-than-light particle cannot be defined in a relativistically invariant way. (orig./HSI)
[en] Recently a definition for a Lorentz invariant operator approximating the d’Alembertian in d-dimensional causal set spacetimes has been proposed. This operator contains several dimension-dependent constants which have been determined for d = 2, …, 7. In this note we derive closed form expressions for these constants, which are valid in all dimensions. Using these we prove that the causal set action in any dimension can be defined through this discrete d’Alembertian, with a dimension independent prefactor. (paper)
[en] A Lorentz-invariant gauge theory for massive fermions on R X S3 spacetime is built up. Using the symmetry of S3, the authors obtain Dirac-type equations and derive the expression of the fermionic propagator. Finally, starting from the SU(N) gauge-invariant Lagrangian, they obtain the set of Dirac-Yang-Mills equations on R X S3 spacetime, pointing out major differences from the Minkowskian case
[en] A sequence of necessary actions for the formulation of free leptonic equations (Dirac algorithm) is established. A complete and closed set of equations for the description of massive and massless, charged and neutral, stable and unstable leptons is obtained within a unified algorithmic approach. The Lorentz invariance and covariance of the newly derived equations is as rigorous as for the Dirac equation. All the established facts together explain the exceptional role of the structure of lepton equations that serves as a carrier of the properties of the observed particles.
[en] This paper reports on the Fourth Meeting on Lorentz and CPT Symmetry, CPT '07, held in August 2007 in Bloomington, IN, USA. The focus is on recent tests of Lorentz symmetry using atomic and optical physics. Results presented at the meeting include improved bounds on Lorentz violation in the photon sector, and the first bounds on several coefficients in the gravity sector
[en] Bipartite Riemann-Finsler geometries with complementary Finsler structures are constructed. Calculable examples are presented based on a bilinear-form coefficient for explicit Lorentz violation.
[en] Taking clues from the recent construction of the covariant action for type II and heterotic string field theories, we construct a manifestly Lorentz covariant action for type IIB supergravity, and discuss its gauge fixing maintaining manifest Lorentz invariance. The action contains a (non-gravitating) free 4-form field besides the usual fields of type IIB supergravity. This free field, being completely decoupled from the interacting sector, has no physical consequence.
[en] In this paper we prove that a class of skew products maps with non uniformly hyperbolic base has exponential decay of correlations. We apply this to obtain a logarithm law for the hitting time associated to a contracting Lorenz attractor at all the points having a well defined local dimension, and a quantitative recurrence estimation.